How Do I Hold the Output States When Downloading to an RSLogix 5000 PLC?

[0hi0 0]

How painful will it be to have to remember to reset the Program Mode state of each output to Hold Last State each time you download to the PLC and then back to Safe State? Our company uses a VPN to change programs on PLCs out in the field. I'm trying to prevent undesirable actions when going back to run mode.

[kaiser_will 65]

I believe one solution is to have two processors that are master-slave, with you downloading first to the slave then switching roles (master becomes slave, and vice-versa). A lot of hot rolling mills (metals) have dual processor setups like this, mainly if one processor chokes the mill keeps running and you don't have an awful mess for the cleanup crew. The real condition you want to have is for outputs to hold state while the program is updated (and the CPU state changes [online/run-offline-program update-online/run]). Can the solution be hard-wired, such as relays sealed in for critical outputs with a PLC output to seal in the relays (carryover control)?

[controlsdude 3]

I take that back, you have a selection of either OFF, ON , or HOLD state while in program mode. Looks like you are good to go! Its on the config tab of the output card

[JeffKiper 9]

You might want to read Ron Beaufort's "Going to run" quiz. With the proper preperantion the changing of a program will not cause problems. Each and every function a PLC or PAC does is known so if you plan for it it will not be an "Oh S#1t" problem.

[BobLfoot 301]

Let me see if I understand this correctly. 1. You have a PLC running a process. 2. The PLC Outputs are configured to goto "Safe State" should the PLC or communication network fail. 3. You maintain the PLC over a VPN and download new programs from time to time. 4. During download you want the outputs to hold last state, rather than take them safe, do the download and start them back up? What flavor of AB PLC are you using? CLGX, PLC5, SLC500?

[0hi0 0]

You are correct sir! RSlogix 5000

[BobLfoot 301]

Given that you are using RSlogix5000 I must ask, why not make use of the copy paste feature and then test edits. If you open an offline copy of your new code and an online copy of your old code you can copy and paste entire routines at once. Another option assuming you have the memory is to place you new code in one routine and your old code in another and toggle the JSR's on/off. Are there reasons why either of these features would not work? There may be the possibility to "automate" the change from last state to safe and vice versa thru the use of SSV Instructions. I'm working thru the Holiday so thats about all I can sugest for now.

[JeffKiper 9]

"I'm working thru the Holiday so thats about all I can sugest for now." Why is it that we are the chosen ones that always get to work the holiday shutdowns? At least I out of the forging for Henry Ford's folks

[Corben 2]

It depends wich PLc you are working with. I wanted to hold the outputs with a compact logix 1768L43 but it didn't work. Off & On too. So i called the Rockwell technical assistance and they told me this function don't work on Compactlogix. With others PLC i don't know.